Probably FFXIII (fun gameplay, brilliant cutscenes, and lengthy single player game). Strange pick but I liked it the most.
Heard good things about RDR and SMG2 but haven't played them yet. I imagine they're both in with a good shot of GOTY.
Played Mass Effect 2 and God of War 3, both outstanding in some areas and very mediocre in others. I can't help but be a tinge disappointed with both given that I was massive fan of their predecessors (e.g. mass effect, and god of war 1 and 2).